1. Field of the Invention
The present invention relates to a capacitor applied to a semiconductor device, for example, a dynamic random access memory (DRAM), and a method of manufacturing the capacitor.
2. Description of the Related Art
In general, a DRAM capacitor is roughly divided into a stack type and a trench type. Conventionally, in a stack type capacitor, a lower electrode serving as a storage electrode and an upper electrode serving as a plate electrode both are composed of a polysilicon layer; and a capacitor insulating film is formed of, for example, a silicon oxide film, an NO film or the like. In addition, in a trench type capacitor, a storage electrode is formed of a polysilicon layer, a plate electrode is formed of an impurity layer implanted in a substrate, and a capacitor insulating film is formed of, for example, a silicon oxide film, a NO film or the like.
With downsizing of the DRAM, there has been a growing demand a capacitor with high performance. In particular, an approach from two aspects, structure and material, has been made for increasing the capacitance of the capacitor. With respect to the structural aspect, for example, there has been a proposal that a stack type capacitor is structured to form a step on the upper electrode and the lower electrode in order to increase the area of a dielectric between the upper electrode and the lower electrode (refer to Jpn. Pat. Appln. KOKAI Publication Nos. 2003-332261 and 6-326267, for example). In addition, with respect to the material aspect, use of a material having a high dielectric constant, such as a Ta2O5 film or a BST film, is discussed (refer to Jpn. Pat. Appln. KOKAI Publication Nos. 2003-332261 and 9-97880, for example).
However, there is a limitation to improving an electrode structure by increasing an area of a dielectric. In order to increase the capacitance of a capacitor, there is a need for achieving a thin, uniform or highly dielectric capacitor insulating film. However, a conventional capacitor insulating film has been formed by a film forming process such as a thermal oxidation technique, a sputtering technique, or a chemical vapor deposition (CVD) technique. Thus, it has been difficult to achieve a thin, uniform, and highly dielectric capacitor insulating film. Therefore, there is a demand for a semiconductor device having a high performance capacitor insulating film which is thin, uniform, and highly dielectric, and for a method of manufacturing the semiconductor device.